User manual HP STORAGEWORKS XP AUTO PATH SOFTWARE

[. . . ] See "Warranty statement" (page 8). 2 HP StorageWorks Auto Path: User's Guide (HP-UX) contents About this guide 5 Revision history 6 Technical support 7 Warranty statement 8 1 Auto Path features 11 ULM services 13 Dynamic load balancing 14 Automatic failover 15 Automatic path recovery 16 System requirements 17 Installation 19 Installing Auto Path software: HP-UX host Uninstalling Auto Path: HP-UX host 21 20 2 Contents 3 3 Command-line interface 23 autopath display 24 autopath help 26 autopath recover 27 autopath retrieve 28 autopath set_lbpolicy 29 autopath set_prefpath 30 Troubleshooting 31 Recovering after a failure 32 Auto Path messages 33 Contacting HP customer service Index 35 4 34 4 HP StorageWorks Auto Path: User's Guide (HP-UX) About this guide The instructions given in this guide are intended for system administrators who already have the following skills and knowledge: · a background in data processing and understanding of direct-access storage device subsystems and their basic functions · familiarity with disk arrays and RAID technology · expertise with the operating system, including commands and utilities Unless otherwise noted, the term disk array refers to any of these disk arrays: HP Surestore Disk Array XP48 HP StorageWorks Disk Array XP128 HP Surestore Disk Array XP256 HP Surestore Disk Array XP512 HP StorageWorks Disk Array XP1024 HP StorageWorks Virtual Array 7100 HP StorageWorks Virtual Array 7400 For information about the disk arrays, please refer to the owner's manuals. About this guide 5 Revision history July 2001 October 2001 Preliminary release for HP-UX. First release for HP-UX 11. 00 and 11. 11. Revised for release 2. 00 for HP-UX with ULM services. July 2002 6 HP StorageWorks Auto Path: User's Guide (HP-UX) Technical support Technical support is provided for this product through an HP Support Contract, purchased at the time you purchased this product. See the HP Support Contract for information about technical support. [. . . ] Auto Path provides enhanced data availability with these features: · automatic path failover to an alternate path · automatic path recovery after failed path is serviced · automatic failback when a path recovers from failure · dynamic load-balancing over multiple paths · command-line user interface (CLI) for Auto Path management · ability to reestablish previous load-balancing policy after reboot through the CLI The HP Auto Path software performs dynamic load balancing of data flow through multiple paths. It detects multiple paths to each logical device and distributes the data load among the paths for optimum performance. The user interface lets a system administrator define load balancing policies and preferred paths, and view device path information. Auto Path manages Auto Path features 11 paths according to the balancing policy, ensuring that no single path is a performance bottleneck. 12 HP StorageWorks Auto Path: User's Guide (HP-UX) ULM services The SCSI Upper Layer Module (ULM) interface is used by Auto Path and similar modules to provide flexible configuration and layering of modules above the SCSI disk drivers. In order for Auto Path to be configured into 11. 0/11. 11 (and coexist with other pseudodrivers) Auto Path must register itself with the ULM services for each LUN path that it wants to control. Auto Path features 13 Dynamic load balancing Auto Path performs dynamic load balancing while monitoring each path to ensure that the I/O transaction is completed. The load balancing policy is selected by the administrator. The dynamic load balancing policy prevents any path from becoming overloaded, and it helps to prevent the congestion that occurs when many I/O operations are directed to common devices along the same path. If a preferred path is used for a device, the entire I/O for that particular device flows through the preferred path and no load balancing is done by Auto Path for that device. VA disk arrays Increased performance is not always realized with Virtual Array systems. In most cases, the best performance is provided by using preferred paths. 14 HP StorageWorks Auto Path: User's Guide (HP-UX) Automatic failover In the event of a failure of any part of a path between the disk array and a server, Auto Path automatically switches to an alternate path, dropping the failed path out of the I/O rotation without any loss of data. The failover is not visible to applications, so normal operation continues without downtime. For troubleshooting information, see "Troubleshooting" (page 31). Auto Path features 15 Automatic path recovery When a path fails, it is no longer used. After the path is returned to normal, Auto Path automatically begins using the path with the designated load balancing policy. If the failed path was set as the preferred path, after the path is recovered, Auto Path automatically begins using the preferred path. No user action is necessary. 16 HP StorageWorks Auto Path: User's Guide (HP-UX) System requirements To install Auto Path, the system must conform to these requirements: · HP-UX 11. 00 or 11. 11 64-bit operating system · administrator root access to the host system · SCSI Upper Layer Module Services installed on the system HP-UX 11. 00: version B. 11. 00. 01 HP-UX 11. 11: version B. 11. 11. 01 For specific installation requirements for your system, contact your HP account representative. Additional information Be sure to view the readme. txt on the Auto Path installation CD-ROM for important information about product limitations. Auto Path features 17 18 HP StorageWorks Auto Path: User's Guide (HP-UX) 2 Installation This chapter describes the procedures for installing Auto Path. Installation of Auto Path software is performed by users with administrator privileges. The HP account representative can assist in determining the supported configurations for your system. Installation 19 Installing Auto Path software: HP-UX host Before installing Auto Path software, ensure that SCSI Upper Layer Module Services is installed on the system. To install Auto Path, you must have superuser (root) access on the HP-UX host. Caution Read the readme. txt file on the installation media for more details about installation. Log on to the HP-UX system as superuser (root). Insert the Auto Path installation CD into the CD-ROM drive. [. . . ] If so, restart the recovery process by executing the autopath recover command. autopath recover (page 27) Related information 32 HP StorageWorks Auto Path: User's Guide (HP-UX) Auto Path messages Auto Path reports errors, diagnostic messages, and informational messages to the /var/adm/syslog/syslog. log file. The user can execute dmesg command to view the messages reported by Auto Path. Auto Path reports the following messages: Event Sample message DEVICE ACCESS FAILURE AUTOPATH: Warning: Unable to access device 0x1f040000 MAXIMUM LUN COUNT LIMIT AUTOPATH: Warning: LUN count reached maximum value of 65536. [. . . ]